Valtteri Bottas has been handed a contract extension at Mercedes which will keep him with the German manufacturer in 2018.

Bottas was the replacement for Nico Rosberg at the start of the season following the world champion's shock retirement from the sport at the end of 2016. The Finnish driver has enjoyed a successful debut year with the team, claiming a maiden pole position in Bahrain and a maiden victory in Russia, following up with a second of each in Austria.

Though Mercedes stalled on offering him a new deal this year, an extension for Bottas has always looked likely, with team boss Toto Wolff often repeating that it was a "no-brainer" he would be retained for another season. The delay was more down to Wolff's pragmatic approach to this year's driver market and the uncertainty over whether Sebastian Vettel would extend his contract at Ferrari, which he did ahead of the Belgian Grand Prix.

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Wolff says Bottas' new deal is just reward for his form alongside Lewis Hamilton this year.

"We gave Valtteri a big challenge this year: joining the team at the eleventh hour, stepping up to the forefront of F1 and pairing with the sport's best driver as his team-mate," Wolff said. "With that in mind, his results have been probably even more impressive. "There have been ups and downs - more ups, fewer downs - and some great highlights like his two race wins in Russian and Austria. Overall, the balance of his performances and his upward trajectory made it a no-brainer for us to continue with him into 2018.

"For our team, the bonus factors are the respect and sportsmanship that have grown between our two drivers. The chemistry and dynamic between Valtteri and Lewis work and are what we need to take the fight to our competitors."

The news confirms that the top three teams -- Mercedes, Ferrari and Red Bull -- will go into 2018 with unchanged line-ups. Bottas remains an outside contender in this year's title fight but is 38 points behind Ferrari's Sebastian Vettel and a further three behind teammate and championship leader Lewis Hamilton.